1. Field of the Invention
The present invention generally relates to the art of electrochemical cells. In particular, the present invention is directed to a method for manufacturing an electrode component for use in an electrochemical cell, and the electrode component so manufactured. More specifically, this invention relates to a process for the manufacture of a cathode component and preferably a carbonaceous cathode component that is formulated in a water-based environment with the aid of a surfactant. Up to now, flammable solvents have been used in such processes to suspend the cathode material and aid in the homogeneous distribution of any added binder material. The present invention eliminates flammable solvents through the use of a water/surfactant combination to wet the cathode and binder materials to form a paste that is easily processible into the desired shape electrode component.
2. Prior Art
The prior art process by which electrode active materials, and particularly carbonaceous materials are formulated for use in electrochemical cells uses a flammable solvent such as isopropyl alcohol. In that manner, suspended in an alcohol-based slurry is thoroughly mixed with a suitable binder material to form a depolarizer admixture paste. In the case of non-carbonaceous electrode active materials, conductive diluents are preferably added to the mix. The alcohol-based solvent serves to suspend the electrode active material in the slurry in addition to aiding in the homogeneous distribution of the binder material throughout the slurry. Alcohol-based solvents have relatively low surface tensions and for that reason are advantageous materials for this application. Particularly, isopropyl alcohol has a surface tension of about 21.7 dynes/cm that enables it to effectively wet the surface area of electrode active materials, especially carbonaceous materials, which have very high surface areas. Pure water, by comparison, has a surface tension of about 72 dynes/cm, and wets the electrode active material very poorly.
Although alcohol-based solvents and particularly isopropyl alcohol perform well as the suspension and dispersion agent in the manufacture of electrodes for use in electrochemical cells, they also have several limitations. Because alcohol-based solvents are flammable, explosion-proof equipment is required in the manufacturing process. In a full scale manufacturing process, quantities of the solvent are large enough that recovery methods must be considered as opposed to losing the material to the atmosphere through evaporation. These factors, as well as the expense of the solvent itself, add significantly to the cost and complexity of the electrode manufacturing process.